1、 1 外文资料原文 DS18B20 1.1DESCRIPTION The DS18B20 Digital Thermometer provides 9 to 12-bit (configurable) temperature readings whichindicate the temperature of the device. Information is sent to/from the DS18B20 over a 1-Wire interface, so that only one wire (and ground)needs to be connected from a centr
2、al microprocessor to a DS18B20. Power for reading, writing, andperforming temperature conversions can be derived from the data line itself with no need for an externalpower source. Because each DS18B20 contains a unique silicon serial number, multiple DS18B20s can exist on thesame 1-Wire bus. This a
3、llows for placing temperature sensors in many different places. Applicationswhere this feature is useful include HVAC environmental controls, sensing temperatures inside buildings,equipment or machinery, and process monitoring and control. 1.2FEATURES (1) Unique 1-WireTM interface requires only onep
4、ort pin for communication (2) Multidrop capability simplifies distributed temperature sensing applications (3) Requires no external components (4) Can be powered from data line. Power supplyrange is 3.0V to 5.5V (5) Zero standby power required (6) Measures temperatures from -55C to+125C. Fahrenheit
5、equivalent is -67F to+257F (7) 0.5 C accuracy from -10C to +85C (8) Thermometer resolution is programmablefrom 9 to 12 bits (9) Converts 12-bit temperature to digital word in750 ms (max.) (10) User-definable, nonvolatile temperature alarmsettings 2 (11) Alarm search command identifies andaddresses d
6、evices whose temperature isoutside of programmed limits (temperaturealarm condition) (12) Applications include thermostatic controls,industrial systems, consumer products,thermometers, or any thermally sensitivesystem 1.3PIN ASSIGNMENT DETAILED PIN DESCRIPTION Table 1 DS18B20Z (8-pin SOIC) and DS18P
7、20P (TSOC): All pins not specified in this table are not to beconnected. 1.4OVERVIEW The block diagram of Figure 1 shows the major components of the DS18B20. The DS18B20 has fourmain data components: 1) 64-bit lasered ROM, 2) temperature sensor, 3) nonvolatile temperature alarmtriggers TH and TL, an
8、d 4) a configuration register. The 3 device derives its power from the 1-Wirecommunication line by storing energy on an internal capacitor during periods of time when the signal lineis high and continues to operate off this power source during the low times of the 1-Wire line until itreturns high to
9、 replenish the parasite (capacitor) supply. As an alternative, the DS18B20 may also be powered from an external 3V - 5.5V supply. DS18B20 BLOCK DIAGRAM Figure 1 Communication to the DS18B20 is via a 1-Wire port. With the 1-Wire port, the memory and controlfunctions will not be available before the R
10、OM function protocol has been established. The master mustfirst provide one of five ROM function commands: 1) Read ROM, 2) Match ROM, 3) Search ROM, 4)Skip ROM, or 5) Alarm Search. These commands operate on the 64-bit lasered ROM portion of eachdevice and can single out a specific device if many are
11、 present on the 1-Wire line as well as indicate tothe bus master how many and what types of devices are present. After a ROM function sequence has beensuccessfully executed, the memory and control functions are accessible and the master may then provideany one of the six memory and control function
12、commands. One control function command instructs the DS18B20 to perform a temperature measurement. The resultof this measurement will be placed in the DS18B20s scratch-pad memory, and may be read by issuing amemory function command which reads the contents of the scratchpad memory. The temperature a
13、larmtriggers TH and TL consist of 1 byte EEPROM each. If the alarm search command is not applied to theDS18B20, these registers may be used as general purpose user memory. The scratchpad also contains aconfiguration byte to set the desired resolution of the temperature to digital conversion. Writing TH, TL,
